DE 198 10 241 C2 has previously disclosed an electromagnetic hydraulic valve establishing the generic type which is designed as a 3/2-way directional control valve and is preferably used in automatic transmissions of motor vehicles. This hydraulic valve consists, on the one hand, of an electromagnet having a coil winding, arranged on a spool, and a magnet housing enclosing the coil winding and, on the other hand, of a hydraulic part having a valve stem which has a pressure connection and also a tank connection and a consumer connection. In this case, the spool of the electromagnet and the valve stem of the hydraulic part are designed as a one-piece plastic body which has an axial longitudinal bore which is formed with different diameters and which is designed on the one hand as an armature space for an axially movable magnet armature and on the other hand as a control region for a closing body connected to the magnet armature. In addition, the magnet housing at the electromagnet of the hydraulic valve continues from its shell enclosing the coil winding into a section which spans the end face of the spool and has an annular collar which projects into that part of the longitudinal bore of the plastic body which is designed as armature space and at the same time forms a top magnet pole of the electromagnet. At the same time, a cylindrical pole core projects from the other side into that part of the longitudinal bore of the plastic body which is designed as armature space, this pole core being held in the longitudinal bore of the plastic body by a push-in plate, which can be pushed laterally into the plastic body and on the ends of which the magnet housing rests, and thus forming together with the push-in plate a magnet pole of the electromagnet, this magnet pole being connected to the magnet housing in a magnetically conductive manner. In this case, the pole core of the bottom magnet pole has an encircling annular groove and the plastic body has a radially continuous slot, into which the push-in plate of U-shaped design is pushed from the outside in such a way that its two legs engage in the annular groove of the pole core. By means of a riveted connection, the magnet housing is then fastened to the ends of the push-in plate, which project from the plastic body on both sides, and at the same time a magnetic connection is produced between the two components.
However, a disadvantage with this known electromagnetic hydraulic valve is that it has no fastening elements at all for fixing the hydraulic valve in a push-in bore, since it is conceived for the control of automatic transmissions in motor vehicles, and such directional control valves generally arranged next to one another in groups are usually fixed together axially in a sandwich arrangement in their push-in bores by a separate pressure plate screwed to the engine. However, directional control valves for controlling a variable valve drive of an internal combustion engine are usually fastened in individual push-in bores on the engine block of the internal combustion engine, so that the known hydraulic valve, for this intended purpose, first has to be provided with additional fastening elements which are designed, for example, like the separate retaining lugs or the like arranged on the magnet housing of the hydraulic valve disclosed in DE 199 37 969 A1. However, such additional fastening elements generally increase the outlay in terms of production and materials for the hydraulic valve and therefore contribute to an adverse increase in its manufacturing costs. This also applies to the pole core, of relatively bulky design, of the bottom magnet pole of the known hydraulic valve, this pole core, due to its mass, not only requiring a considerable amount of material but also adversely increasing the weight of the hydraulic valve as a result. In addition, in the case of the known hydraulic valve, the two-piece design of the bottom magnet pole of the electromagnet has proved to be disadvantageous to the effect that the desired ease of fitting of the push-in plate on the hydraulic valve requires greater tolerances between the push-in plate and the annular groove in the pole core, and therefore larger air gaps form between the magnetic-flux transfer areas, which are relatively small anyway, of both components, and these air gaps impair even further the magnetic transfer of the lines of force between both components.